Pictures promoting the new series of Merlin have been released by the BBC.

The 13-part run starts on BBC One on Saturday 6th October at 7.45pm with the first episode of a two-part story called Arthur's Bane. Colin Morgan is Merlin, with Bradley James as King Arthur, Angel Coulby as Gwen, Katie McGrath as Morgana, Richard Wilson as Gaius, and John Hurt as the voice of the Great Dragon. Special guest stars in the new series will include Liam Cunningham as Ruadan, Sophie Rundle as Sefa, and Alex Vlahos as Mordred.

Mini-synopses of the two episodes are given below:

Three years on from the end of Series 4, Arthur has never felt stronger, with Queen Guinevere and the Knights of the Round Table at his side.

Camelot basks in the halcyon days of a new golden age. But even as she flowers, so the dark seeds of her destruction are being sown, for in the frozen wastelands of the north, men are disappearing without trace.

In search of answers, King Arthur and his Knights must undertake a dangerous mission to the unknown. As the sun sets on the icy plains, Merlin finds himself locked in a battle unlike any he has fought before - a battle with fate itself.

Episode 2 is currently scheduled for 7.45pm on Saturday 13th October.

Ancient prophecies of Mordred weigh heavy on Merlin, for not even he can sway Arthur from his chosen path.

As dawn breaks across the icy tundra, Merlin and Arthur are close to exhaustion. With each tortured step, the fortress of Ismere looms ever nearer and Merlin's fear intensifies. What game is Mordred playing? And what powerful secrets are Morgana and the druid Ruadan searching for amongst its twisted catacombs?

It seems like this time not even Merlin can stop Arthur from walking right into the lion's den. For in this bleak and transient wilderness, only one thing is certain: the great trial for Albion has finally begun.